Part 1 of this proposal deals with three principles of categorization: (1) the Classical principle, where categorization is based on features common to all members of a class; (2) the Prototype principle, where categorization considers many features that are only correlated with class membership; and (3) the Exemplar principle, where categorization is based on stored exemplars of various categories. Specific models based on the three principles are developed and tested in the proposed experiments. Some experiments focus on a successful model of a particular principle--e.g., the Cue Validity model used by Eleanor Rosch--and subject it to new empirical tests. Other studies compare models generated by the same principle to determine the best way to instantiate a particular principle. Other studies compare models based on the prototype principle with those based on the Exemplar principle, in an effort to determine (a) the relative efficacy of the two principles and (b) the factors that encourage the use of one principle rather than another. The remaining studies focus on the Classical principle, and try to determine why models based on this principle have failed in recent studies of categorization. The content issues investigated in these four kinds of studies include: discrete vs. continuous prototypes, the role of specific exemplars in categorization, and the nature of basic-level categories. Part 2 of the proposal deals with interference and integration effects in sentence-memory. Many theories of memory (e.g., Anderson and Bower's HAM model) hold that the more facts learned about a concept, the greater the interference in retrieving any particular facts. Some proposed studies explore the beneficial effects of integration further, while others deal with an analysis of integration effects in terms of scripts, as proposed by Schank and Abelson.